1. Field of the Invention
This invention relates to number imprinting devices, and more particularly, to number imprinting devices forming a part of an offset printing press including a blanket cylinder and an impression cylinder.
2. Description of the Prior Art
In the printing business, offset printing presses are used to print multiple copies of tickets, invoices, multi-part forms and various other documents. It is frequently desirable to sequentially number each separate document in a group of documents to specifically identify each otherwise identical duplicate document. Conventional offset printing press equipment has no capability for imprinting a sequential group of numbers onto a series of identical documents.
When a print shop owner is called upon to sequentially number a group of duplicate documents, a variety of different types of equipment may be utilized. One type of equipment is placed in series with the feed side or paper input side of the offset printing press and sequentially numbers each paper sheet before it is fed into the offset printing press and imprinted with the desired image. Other types of prior art numbering equipment operate on the delivery side of the offset printing press and sequentially number documents after they have been printed by the offset printing press. Other types of equipment which are unrelated to either the input or output stream of the offset printing press may be used to imprint numbers on a group of identical documents. Documents to be numbered are fed one at a time into such equipment which is then manually actuated by a foot switch or related device. Such one at a time, manually fed numbering operations are slow, time consuming and costly to the customer. The registration characteristics of such equipment is comparatively poor in that the position of the numbers imprinted on each documents typically vary by a significant distance since the equipment is unable to position each document into a fixed location on a repeatable basis.
In the past, one organization manufactured an offset printing press which could be converted back and forth between an image printing device and a numbering device. In order to accomplish this conversion, the blanket was physically removed from the blanket cylinder, a number head was secured within the recessed section of the blanket cylinder, and a cylindrical metal ink roller was firmly clamped into a fixed position in proximity to the number imprinting surface of the number head to reink the number head after each revolution of the blanket cylinder. When number operations had been completed, the number head and inking roller assembly was removed from the printing press and the blanket was reinstalled on the printing press. A second cylindrical roller was secured adjacent to the ink roller to distribute printer's ink onto the surface of the ink roller. Approximately thirty minutes was required to either remove the blanket and install the numbering device or to reconvert the unit to a printing press by removing the numbering and inking mechanism and reinstalling the blanket. The total numbering system installation and removal process required one hour. Use of this numbering system required removal of the blanket since otherwise the ink roller would ink both the number head and the entire blanket and cover the entire image receiving surface of each document with ink. This attachment for converting an offset printing press into a number imprinting device was never commercially accepted as a result of the extensive time and effort required to convert the device between an offset printing press and a number imprinting device, resulting in substantial, costly press down time.